Titanyl phthalocyanine crystal and production method of the same, and electrophotosensitive material and production method of the same

ABSTRACT

The present invention relates to a titanyl phthalocyanine crystal having excellent storage stability of coating solution, to satisfy that (a) the crystal does not have a peak of a change in temperature except for a peak associated with evaporation of adsorbed water in differential scanning calorimetry or that (b) the crystal recovered after dipping in an organic solvent for 24 hours at least a maximum peak at a Bragg angle 2θ±0.2°=27.2° and has no peak at 26.2° in a CuK α characteristic X-ray diffraction spectrum, and a method of producing the same; and an electrophotosensitive material using the above crystal, and a method of producing the same.

BACKGROUND OF THE INVENTION

The present invention relates to a novel titanyl phthalocyanine crystal formed from a titanyl phthalocyanine compound. The present invention also relates to a method of producing the titanyl phthalocyanine crystal. The present invention also relates to an electrophotosensitive material using the titanyl phthalocyanine crystal as an electric charge generating material. The present invention further relates to a method of producing the electrophotosensitive material.

Electrophotosensitive materials are used in image forming apparatuses such as electrostatic copying machine, laser printer and plain paper facsimile.

As the electrophotosensitive material, a so-called organic photosensitive material formed by using the following components in combination has widely been used.

Electric charge generating material which are irradiated with light to generate electric charges (holes and electrons).

Electric charge transferring material for transferring the generated electric charges, which is classified into a hole transferring material for transferring holes and an electron transferring material for transferring electrons.

Binding resin having a film forming property.

The organic photosensitive material has such an advantage that it is easily produced as compared with an inorganic photosensitive material using an inorganic semiconductor material.

The organic photosensitive material also has advantages such as wide range of choice of materials such as electric charge generating material, electric charge transferring material and binding resin, and high functional design freedom.

The organic photosensitive material is produced by forming a single-layer or multi-layer type photosensitive material on a conductive substrate.

The single-layer type photosensitive layer is formed by dispersing an electric charge generating material in a binding resin, together with an electric charge transferring material (hole transferring material and/or electron transferring material).

The multi-layer type photosensitive layer is formed by laminating an electric charge generating layer containing an electric charge generating material and an electric charge transferring layer containing an electric charge transferring material (hole transferring material or electron transferring material) in this order or a reverse order.

As the electric charge generating material, for example, various pigments can be used according to the sensitivity range of the photosensitive material.

As the electric charge generating material for photosensitive material which is sensitive to infrared or near infrared light emitted from a semiconductor laser or infrared LED, for example, phthalocyanine pigments have widely been used.

The phthalocyanine pigment varies depending on the chemical structure and includes, for example, metal-free phthalocyanine compound, copper phthalocyanine and titanyl phthalocyanine. The respective compounds can be in various crystal forms.

Therefore, crystals having various crystal forms of various phthalocyanine compounds have been studied by a lot of investigators to find out optimum crystals suited best for use as the electric charge generating material.

For example, Japanese Patent No. 2907121 discloses that a crystal having a Y type crystal form of titanyl phthalocyanine is superior in sensitivity characteristics for electric charge generating material to a crystal having the other crystal form and can contribute to an improvement in sensitivity of the electrophotosensitive material.

A coating solution for the single-layer type photosensitive layer, or a coating solution for electric charge generating layer of the multi-layer type photosensitive layer using the Y type titanyl phthalocyanine crystal can be prepared by adding the crystal and other components in an organic solvent and uniformly dispersing them.

The layer formed by coating the coating solution on the substrate immediately after preparation or within about 60 minutes, and drying the coating solution is particularly superior in sensitivity characteristics as described in the above publication.

As is apparent from the present inventors' study, the sensitivity characteristics of the layer, which was formed by coating the coating solution after storage for a fixed time (e.g. 24 hours) and drying the coating solution, is drastically lowered as compared with the layer formed by using the coating solution immediately after preparation.

It has been found that, since the coating solution prepared by using the Y type titanyl phthalocyanine crystal described in the above publication is inferior in storage stability, the photosensitive layer having good sensitivity characteristics can not be formed stably.

SUMMARY OF THE INVENTION

A main object of the present invention is to provide a novel titanyl phthalocyanine crystal capable of preparing a coating solution having excellent storage stability, which can stably form a photosensitive layer having good sensitivity characteristics.

Another object of the present invention is to provide a method of producing the titanyl phthalocyanine crystal.

Still another object of the present invention is to provide an electrophotosensitive material having excellent sensitivity characteristics using the titanyl phthalocyanine crystal, and a method of producing the same.

To attain the objects described above, the present inventors has studied about the cause of deterioration of the storage stability using a conventional Y type titanyl phthalocyanine crystal described above. As a result, they have found the following fact.

A conventional Y type titanyl phthalocyanine crystal has poor stability in an organic solvent contained in the coating solution, for example, tetrahydrofuran. Therefore, a crystal transfer is liable to occur, that is, the Y type crystal form is gradually changed into the β type crystal with poor sensitivity characteristics during the storage of the coating solution in a fixed period. Therefore, the longer the lapsed time after preparation, the inferior the sensitivity characteristics of the layer formed by using such a coating solution tend to become.

Therefore, the present inventors have studied about the physical properties to improve the stability of the titanyl phthalocyanine in the organic solvent.

As a result, they have found that the titanyl phthalocyanine crystal satisfying at least one of the following two physical properties (a) and (b) is superior in stability in the organic solvent to a conventional Y type titanyl phthalocyanine crystal and hardly causes crystal form changing, as is apparent from the results of the Examples and Comparative Examples described below, so that a coating solution having excellent storage stability can be formed. Thus, the present invention has been completed.

(a) The crystal does not have a peak of a change in temperature within a range from 50 to 400° C. except for a peak associated with evaporation of adsorbed water in differential scanning calorimetry.

(b) The crystal recovered after dipping in an organic solvent for 24 hours has at least a maximum peak at a Bragg angle 2θ±0.2°=27.2° and has no peak at 26.2° in a CuK α characteristic X-ray diffraction spectrum.

The titanyl phthalocyanine crystal of the present invention can be produced by the production method of the present invention, which comprises the following steps:

a pigmentation pretreatment step of adding a titanyl phthalocyanine in an aqueous organic solvent, stirring under heating for a fixed time, and allowing the resulting solution to stand for a fixed time under the conditions at a temperature lower than that of the above stirring process, thereby to stabilize the solution; and

a pigmentation step of removing the aqueous organic solvent from the solution to obtain a crude crystal of the titanyl phthalocyanine, dissolving the crude crystal in a solvent, adding dropwise the solution in a poor solvent to recrystallize the titanyl phthalocyanine compound, and then subjecting the recrystallized compound to milling treatment in a non-aqueous solvent in the presence of water.

The titanyl phthalocyanine crystal of the present invention can be produced by other production methods which comprise the following steps:

a pigmentation pretreatment step of adding a titanyl phthalocyanine in an aqueous organic solvent, stirring under heating for a fixed time, and allowing the resulting solution to stand for a fixed time under the conditions at a temperature lower than that of the above stirring process, thereby to stabilize the solution;

a step of removing the aqueous organic solvent from the solution to obtain a crude crystal of the titanyl phthalocyanine, and treating the crude crystal according to acid-paste method; and

a step of subjecting a low-crystalline titanyl phthalocyanine compound obtained by the above steps to milling treatment, with water contained therein.

The electrophotosensitive material of the present invention comprises a photosensitive layer containing the titanyl phthalocyanine crystal of the present invention as the electric charge generating material.

Examples of the photosensitive layer include:

(A) a single-layer type photosensitive layer containing the titanyl phthalocyanine crystal and at least one of a hole transferring material and an electron transferring material in a binding resin; and

(B) a multi-layer type photosensitive layer comprising an electric charge generating layer containing the titanyl phthalocyanine crystal and an electric charge transferring layer containing one of a hole transferring material and an electron transferring material, which are mutually laminated.

The electrophotosensitive material of the present invention can attain good sensitivity characteristics, that are always stable regardless of the lapsed time after preparing the coating solution.

The titanyl phthalocyanine crystal of the present invention can retain a crystal form stably in the photosensitive layer even after preparing the photosensitive material. Therefore, the photosensitive material can retain good sensitivity characteristics, that are stable with a lapse of time, without lowering the sensitivity characteristics on use.

Another photosensitive material of the present invention is characterized in that the titanyl phthalocyanine crystal recovered after isolating from the photosensitive layer and dipping in tetrahydrofuran for 24 hours under the conditions of a temperature of 23±1° C. and a relative humidity of 50 to 60% has at least a maximum peak at a Bragg angle 2θ±0.2°=27.2° and an intensity of a peak at 26.2° does not exceed the intensity of the maximum peak in a CuK α characteristic X-ray diffraction spectrum.

Further, according to the production method of the present invention, which comprises the following steps, it is possible to produce an electrophotosensitive material comprising said single-layer type or multi-layer type photosensitive layer, which attains good sensitivity characteristics that are always stable regardless of the lapsed time after preparing a coating solution.

(Single-layer Type)

A step of preparing a coating solution by adding a titanyl phthalocyanine crystal and other components in an organic solvent, and

a step of forming a single-layer type photosensitive layer by coating the coating solution, followed by drying.

(Multi-layer Type)

A step of preparing a coating solution by adding a titanyl phthalocyanine crystal and a binding resin in an organic solvent, and

a step of forming an electric charge generating layer by coating the coating solution, followed by drying.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the results of differential scanning calorimetry of the titanyl phthalocyanine crystal obtained in Preparation Example 1 according to the present invention.

FIG. 2 is a graph showing a CuK α characteristic X-ray diffraction spectrum of the titanyl phthalocyanine crystal of Preparation Example 1 immediately after synthesis.

FIG. 3 is a graph showing a CuK α characteristic X-ray diffraction spectrum measured again after dipping the titanyl phthalocyanine crystal of Preparation Example 1 in tetrahydrofuran for 24 hours.

FIG. 4 is a graph showing the results of differential scanning calorimetry of the titanyl phthalocyanine crystal obtained in Preparation Example 2.

FIG. 5 is a graph showing a CuK α characteristic X-ray diffraction spectrum of the titanyl phthalocyanine crystal of Preparation Example 2 immediately after synthesis.

FIG. 6 is a graph showing a CuK α characteristic X-ray diffraction spectrum measured again after dipping the titanyl phthalocyanine crystal of Preparation Example 2 in tetrahydrofuran for 24 hours.

FIG. 7 is a graph showing the results of differential scanning calorimetry of the titanyl phthalocyanine crystal obtained in Preparation Example 3.

FIG. 8 is a graph showing a CuK α characteristic X-ray diffraction spectrum of the titanyl phthalocyanine crystal of Preparation Example 3 immediately after synthesis.

FIG. 9 is a graph showing a CuK α characteristic X-ray diffraction spectrum measured again after dipping the titanyl phthalocyanine crystal of Preparation Example 3 in tetrahydrofuran for 24 hours.

FIG. 10 is a graph showing the results of differential scanning calorimetry of the titanyl phthalocyanine crystal obtained in Preparation Example 4.

FIG. 11 is a graph showing a CuK α characteristic X-ray diffraction spectrum of the titanyl phthalocyanine crystal of Preparation Example 4 immediately after synthesis.

FIG. 12 is a graph showing a CuK α characteristic X-ray diffraction spectrum measured again after dipping the titanyl phthalocyanine crystal of Preparation Example 4 in tetrahydrofuran for 24 hours.

FIG. 13 is a graph showing the results of differential scanning calorimetry of the titanyl phthalocyanine crystal obtained in Preparation Example 5.

FIG. 14 is a graph showing a CuK α characteristic X-ray diffraction spectrum of the titanyl phthalocyanine crystal of Preparation Example 5 immediately after synthesis.

FIG. 15 is a graph showing a CuK α characteristic X-ray diffraction spectrum measured again after dipping the titanyl phthalocyanine crystal of Preparation Example 5 in tetrahydrofuran for 24 hours.

FIG. 16 is a graph showing the results of differential scanning calorimetry of the titanyl phthalocyanine crystal obtained in Preparation Example 6.

FIG. 17 is a graph showing a CuK α characteristic X-ray diffraction spectrum of the titanyl phthalocyanine crystal of Preparation Example 6 immediately after synthesis.

FIG. 18 is a graph showing a CuK α characteristic X-ray diffraction spectrum measured again after dipping the titanyl phthalocyanine crystal of Preparation Example 6 in tetrahydrofuran for 24 hours.

FIG. 19 is a graph showing a CuK α characteristic X-ray diffraction spectrum of the titanyl phthalocyanine crystal of Preparation Example 1 isolating from the photosensitive layer of the photosensitive material produced in Example 1 immediately after isolation.

FIG. 20 is a graph showing a CuK α characteristic X-ray diffraction spectrum measured again after dipping the isolating titanyl phthalocyanine crystal of Preparation Example 1 in tetrahydrofuran for 24 hours.

FIG. 21 is a graph showing a CuK α characteristic X-ray diffraction spectrum of the titanyl phthalocyanine crystal of Preparation Example 3 isolating from the photosensitive layer of the photosensitive material produced in Comparative Example 1 immediately after isolation.

FIG. 22 is a graph showing a CuK α characteristic X-ray diffraction spectrum measured again after dipping the isolating titanyl phthalocyanine crystal of Preparation Example 3 in tetrahydrofuran for 24 hours.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described below.

<Titanyl Phthalocyanine Crystal and Method of Producing the Same>

As described above, the titanyl phthalocyanine crystal of the present invention satisfies at least one of two physical properties (a) and (b):

(a) The crystal does not have a peak of a change in temperature within a range from 50 to 400° C. except for a peak associated with evaporation of adsorbed water in differential scanning calorimetry, and

(b) The crystal recovered after dipping in an organic solvent for 24 hours at least a maximum peak at a Bragg angle 2θ±0.2°=27.2° and has no peak at 26.2° in a CuK α characteristic X-ray diffraction spectrum.

The titanyl phthalocyanine crystal is a crystal of a titanyl phthalocyanine compound which is represented by the formula (1):

wherein X¹, X², X³ and X⁴ are the same or different and each represents a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group, and a, b, c and d are the same or different and each represents an integer of 0 to 4, and which has a Y type crystal form or a crystal form that closely resembles the Y type crystal form. Preferred is a titanyl phthalocyanine crystal which has at least a maximum peak at a Bragg angle 2θ±0.2°=27.2° and has no peak at 26.2° in a CuK α characteristic x-ray diffraction spectrum measured by using, as a radiation source, CuK α having a wavelength of 1.541 Å that is a characteristic X-ray of copper.

The organic solvent in which the crystal is dipped in the term (b) includes, tetrahydrofuran, toluene, dichloromethane 1,4-dioxane and a mixture thereof.

The dipping in the organic solvent as the standard for evaluation of the stability of the crystal may be conducted under the same conditions as those in case of actually storing the coating solution. For example, the coating solution is preferably allowed to stand in a closed system under the conditions of a temperature of 23±1° C. and a relative humidity of 50 to 60%.

The halogen atom corresponding to X¹ to X⁴ in the general formula (1) includes, for example, fluorine, chlorine, bromine and iodine. The alkyl group includes, for example, alkyl groups having 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl and hexyl. The alkoxy group includes, for example, alkoxy groups having 1 to 6 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy and hexyloxy.

Preferable examples of the titanyl phthalocyanine compound include compounds represented by the formula

wherein X represents a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group; and e represents an integer of 0 to 4; provided that X¹ to X⁴ in the general formula (1) represent the same X, and a to d, each showing the substitution number, represent the same number e. Among these compounds, a non-substituted titanyl phthalocyanine represented by the formula (11-1)

is used most preferably.

To produce a titanyl phthalocyanine crystal which is represented by the general formula (11) and satisfies at least one of physical properties (a) and (b), phthalonitrile or a derivative (11 a) thereof is first reacted with a titanium alkoxide (11 b) as shown in the following reaction scheme:

wherein X and e are as defined above, and R represents the same alkyl group having 1 to 6 carbon atoms and n-butyl is particularly preferred, or 1,3-diiminoindoline or a derivative (11c) thereof is reacted with a titanium alkoxide (11b) as shown in the following reaction scheme:

wherein X and e are as defined above, and R represents the same alkyl group having 1 to 6 carbon atoms and n-butyl is particularly preferred, thereby to synthesize a titanyl phthalocyanine compound (11).

Then, the titanyl phthalocyanine compound (11) is subjected to a pigmentation pretreatment, which comprises the steps of adding the titanyl phthalocyanine compound in an aqueous organic solvent, stirring under heating for a fixed time, and allowing the resulting solution to stand for a fixed time under the conditions at a temperature lower than that of the above stirring process, thereby to stabilize the solution.

The water-soluble organic solvent used in the pigmentation pretreatment includes, for example, alcohols such as methanol, ethanol and isopropanol; N,N-dimethylformamide, N,N-dimethylacetamide, propionic acid, acetic acid, N-methylpyrrolidone and ethylene glycol; or a mixture thereof. A small amount of a water-insoluble organic solvent may also be added in the water-soluble organic solvent.

The conditions of the stirring treatment among the pigmentation pretreatment are not specifically limited, but the stirring treatment is preferably conducted under the temperature-constant conditions of a temperature within a range from about 70 to 200° C. for about 1 to 3 hours.

The conditions of the stabilization treatment after the stirring treatment are not also specifically limited, but the solution is preferably stabilized by allowing to stand under the temperature-constant conditions of a range within a range from about 10 to 50° C., preferably at room temperature (23±1° C.), for about 5 to 10 hours.

After the completion of the pigmentation pretreatment, a crude crystal of the titanyl phthalocyanine compound obtained by removing the water-soluble organic solvent is pigmentated by dissolving the crude crystal in a solvent according to a conventional method, and adding dropwise the solution in a poor solvent, followed by steps of filtration, washing, milling treatment, filtration and drying, thus producing the titanyl phthalocyanine crystal which satisfies the above physical properties (a) and (b).

Milling treatment comprises the steps of dispersing a solid after washed without drying, in non-aqueous solvent, with water contained therein, and stirring.

Examples of the solvent which dissolves the crude crystal include halogenated-hydrocarbon such as dichloromethane, chloroholm, ethyl bromide and butyl bromide; trihaloacetic acid such as trifluoroacetic acid, trichloroacetic acid and tribromoacetic acid; and sulfuric acid. These solvents can be used alone or two or more kinds of them can be used in combination.

Examples of the poor solvent used for recrystallization include water and an aqueous organic solvent. The aqueous organic solvent includes alcohol such as methanol, ethanol and isopropanol; acetone and dioxane. These solvents can be used alone or two or more kinds of them can be used in combination.

Examples of the non-aqueous solvent used in milling treatment include halogenated-solvent such as chlorobenzene and dichloromethane.

The titanyl phthalocyanine crystal of the present invention can be also produced by the following method.

Namely, after the completion of the pigmentation pretreatment, a crude crystal of the titanyl phthalocyanine compound obtained by removing an aqueous organic solvent is treated according to acid-paste method, which comprises the steps of dissolving the crude crystal in acid, and adding dropwise the solution in water under ice-cooling, followed by stirring the resulting solution for a fixed time and allowing to stand at room temperature (23±1° C.), thereby to recrystallize the solution.

Then, a low crystalline titanyl phthalocyanine compound obtained by the above steps is subjected to said milling treatment of filtrating the compound, washing without drying, and dispersing the resulting solid in non-aqueous solvent, with water contained therein.

The resulting solution is filtered, and then the resulting solid is drying, whereby producing the titanyl phthalocyanine crystal which satisfies the above physical properties (a) and (b).

Examples of the acid used for acid-paste method include concentrated sulfuric acid and sulfonic acid. The non-aqueous solvent used in milling treatment is the same as described above.

<Electrophotosensitive Material and Method of Producing the Same>

The electrophotosensitive material of the present invention is characterized in that a photosensitive layer containing the above titanyl phthalocyanine crystal of the present invention as the electric charge generating material on a conductive substrate.

Another electrophotosensitive material of the present invention is characterized in that, when a titanyl phthalocyanine crystal isolated from the photosensitive layer is dipped in a closed system under the conditions of a temperature of 23±1° C. and a relative humidity of 50 to 60% for 24 hours and the CuK α characteristic X-ray diffraction spectrum of the recovered titanyl phthalocyanine crystal is measured, the titanyl phthalocyanine crystal has at least a maximum peak at a Bragg angle 2θ±0.2°=27.2° and an intensity of a peak at 26.2° does not exceed the intensity of the maximum peak.

It is considered that the titanyl phthalocyanine crystal having an intensity of the peak at a Bragg angle 2θ±0.2°=26.2°, which exceeds the intensity of the maximum peak (27.2°) after dipping for 24 hours, does not retain the crystal form stably after the production of the photosensitive material. Therefore, the photosensitive material using such a titanyl phthalocyanine can not retain good sensitivity characteristics that are stable with a lapse of time.

To isolate the titanyl phthalocyanine crystal from the photosensitive layer, the photosensitive layer peeled from the substrate may be dissolved in tetrahydrofuran, followed by decantation or filtration of the solution.

The photosensitive layer includes so-called single-layer type and multi-layer type photosensitive layers, but the present invention can be applied to both of them.

The single-layer type photosensitive layer is formed by coating a coating solution prepared by dissolving or dispersing a titanyl phthalocyanine crystal as the electric charge generating material in a suitable organic solvent, together with an electric charge transferring material and a binding resin, on a conductive substrate by a coating means, followed by drying. Such a single-layer type photosensitive layer has a simple layer construction and is superior in productivity.

As the electric charge transferring material, for example, the electron transferring materials and/or hole transferring materials can be used. Particularly, the single-layer type photosensitive layer using both transferring materials in combination has an advantage that it can be applied to any of positive and negative charging with a single construction.

Preferable electron transferring material includes, for example, those capable of extracting electrons generated in the titanyl phthalocyanine crystal from the crystal and transferring them efficiently because of good matching with the titanyl phthalocyanine crystal. Similarly, preferable hole transferring material includes, for example, those capable of extracting holes generated in the titanyl phthalocyanine crystal from the crystal and transferring them efficiently because of good matching with the titanyl phthalocyanine crystal.

In the system where the electron transferring material and hole transferring material coexist, it is necessary to consider the combination of both transferring materials to prevent lowering of the electric charge transferability of the whole photosensitive layer, resulting in lowering of the sensitivity of the photosensitive material. Therefore, it is preferred to select the combination of both transferring materials, even if both materials are contained in the same layer in high concentration where hole transfer and electron transfer occur efficiently, a charge transfer complex is not formed.

The multi-layer type photosensitive layer is formed by forming an electric charge generating layer containing a titanyl phthalocyanine crystal using a means such as vacuum deposition method or coating method, coating a coating solution containing an electric charge transferring material and a binding resin on the electric charge generating layer, and drying the coating solution to form an electric charge transferring layer.

To the contrary, the electric charge transferring layer may be formed on the conductive substrate, followed by formation of the electric charge generating layer thereon.

Since the electric charge generating layer has a very thin film thickness as compared with the electric charge transferring layer, it is preferred that the electric charge generating layer is formed on the conductive substrate and the electric charge transferring layer is formed thereon to protect the electric charge generating layer.

The charging type (positively or negatively charging) of the multi-layer type photosensitive layer is selected depending on the formation order of the electric charge generating layer and electric charge transferring layer and the kinds of the electric charge transferring material used in the electric charge transferring layer.

In the layer construction where the electric charge generating layer is formed on the conductive substrate and the electric charge transferring layer is formed thereon, when using the hole transferring material as the electric charge transferring material of the electric charge transferring layer, the photosensitive layer becomes a negatively charging type. In this case, the electron transferring material may be contained in the electric charge generating layer. Preferable electron transferring material to be contained in the electric charge generating layer includes, for example, those capable of extracting electrons generated in the titanyl phthalocyanine crystal from the crystal and transferring them efficiently because of good matching with the titanyl phthalocyanine crystal.

In the above layer construction, when using the electron transferring material as the electric charge transferring material of the electric charge transferring layer, the photosensitive layer becomes a positively charging type. In this case, the hole transferring material may be contained in the electric charge generating layer. Preferable hole transferring material to be contained in the electric charge generating layer includes, for example, those capable of extracting holes generated in the titanyl phthalocyanine crystal from the crystal and transferring them efficiently because of good matching with the titanyl phthalocyanine crystal.

As the electron transferring material, there can be used any of various electron transferring compounds which have conventionally been known.

Examples of the electron transferring material, that can be used preferably, include electron attractive compounds such as benzoquinone compound, diphenoquinone compound, naphthoquinone compound, malononitrile, thiopyran compound, tetracyanoethylene, 2,4,8-trinitrothioxanthone, fluorenone compound [e.g. 2,4,7-trinitro-9-fluorenone], dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, succinic anhydride, maleic anhydride, dibromomaleic anhydride, 2,4,7-trinitrofluorenoneimine compound, ethylated nitrofluorenoneimine compound, tryptoanthrine compound, tryptoanthrineimine compound, azafluorenone compound, dinitropyridoquinazoline compound, thioxanthene compound, 2-phenyl-1,4-benzoquinone compound, 2-phenyl-1,4-naphthoquinone compound, 5,12-naphthacenequinone compound, α-cyanostilbene compound, 4′-nitrostilbene compound, and salt of anion radical of benzoquinone compound and cation. These electron transferring materials can be used alone, or two or more kinds of them can be used in combination.

Among these electron transferring materials, any of compounds represented by the following formulas (ET-1) to (ET-6) is particularly preferably used as the electron transferring material having excellent electron transferability and good matching with the titanyl phthalocyanine crystal.

As the hole transferring material, there can be used any of various hole transferring compounds which have conventionally been known. Examples of the hole transferring material, that can be used preferably, include bendizine compound, phenylenediamine compound, naphthylenediamine compound, phenanthrylenediamine compound, oxadiazole compound [e.g. 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole], styryl compound [e.g. 9-(4-diethylaminostyryl)anthracene], carbazole compound [e.g. poly-N-vinylcarbazole], organopolysilane compound, pyrazoline compound [e.g. 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline], hydrazone compound, triphenylamine compound, indole compound, oxazole compound, isoxazole compound, thiazole compound, thiadiazole compound, imidazole compound, pyrazole compound, triazole compound, butadiene compound, pyrene-hydrazone compound, acrolein compound, carbazole-hydrazone compound, quinoline-hydrazone compound, stilbene compound, stilbene-hydrazone compound and diphenylenediamine compound. These hole transferring materials can be used alone, or two or more kinds of them can be used in combination.

Among these hole transferring materials, any of compounds represented by the following formulas (HT-1) to (HT-17) is particularly preferably used as the hole transferring material having excellent hole transferability and good matching with the titanyl phthalocyanine crystal.

The binding resin include, for example, thermoplastic resins such as styrene polymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic resin, styrene-acrylic copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, polycarbonate, polyallylate, polusulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin and polyether resin; crosslinkable thermosetting resins such as silicone resin, epoxy resin, phenol resin, urea resin and melamine resin; and photocurable resins such as epoxy acrylate and urethane acrylate. These binding resins can be used alone, or two or more kinds of them can be used in combination.

In addition to the above respective components, various additives such as fluorene compounds, ultraviolet absorbers, plasticizers, surfactants and leveling agents can be added to the photosensitive layer. To improve the sensitivity of the photosensitive layer, for example, sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the electric charge generating material.

To control the sensitivity range of the photosensitive material, other electric charge generating materials may be used in combination. The other electric charge generating agent includes, but is not specifically limited to, powders of inorganic photoconductive materials such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and α-silicon; azo pigment, bis-azo pigment, perylene pigment, anthanthrone pigment, conventional phthalocyanine pigment other than titanyl phthalocyanine crystal of the present invention, indigo pigment, triphenylmethane pigment, threne pigment, toluidine pigment, pyrrazoline pigment, quinacridone pigment, dithioketopyrrolopyrrole pigment and a mixture thereof.

In the multi-layer type photosensitive layer, the electric charge generating material and binding resin, which constitute the electric charge generating layer, can be incorporated in various ratios, but the electric charge generating material is preferably incorporated in the amount within a range from 5 to 1000 parts by weight, and preferably from 30 to 500 parts by weight, based on 100 parts by weight of the binding resin.

When using the titanyl phthalocyanine crystal alone as the electric charge generating material, the amount of the electric charge generating material is an amount of the titanyl phthalocyanine crystal. When using the titanyl phthalocyanine crystal in combination with the other electric charge generating material, the amount of the electric charge generating material is a total amount of them.

When using the titanyl phthalocyanine crystal in combination with the other electric charge generating material, the other electric charge generating material is preferably used in a small amount as far as the effect of the titanyl phthalocyanine crystal is not prevented. Specifically, the other electric charge generating material is preferably incorporated in the amount of 30 parts by weight or less based on 100 parts by weight of the titanyl phthalocyanine crystal.

The electric charge transferring material and binding resin, which constitute the electric charge transferring layer, can be incorporated in various ratios as far as the transfer of the electric charges is not prevented and crystallization does not occur. The electric charge transferring material is preferably incorporated in the amount within a range from 10 to 500 parts by weight, and particularly from 25 to 200 parts by weight, based on 100 parts by weight of the binding resin, so that the electric charges generated by light irradiation in the electric charge generating layer can be transferred easily.

With respect to a thickness of the multi-layer type photosensitive layer, the electric charge generating layer is preferably formed in the thickness within a range from about 0.01 to 5 μm, and particularly from about 0.1 to 3 μm, while the electric charge transferring layer preferably formed in the thickness within a range from about 2 to 100 μm, and particularly from about 5 to 50 μm.

In the single-layer type photosensitive layer, the electric charge generating material is preferably incorporated in the amount within a range from 0.1 to 50 parts by weight, and particularly from 0.5 to 30 parts by weight, based on 100 parts by weight of the binding resin, while the electric charge transferring material is preferably incorporated in the amount within a range from 20 to 500 parts by weight, and particularly from 30 to 200 parts by weight, based on 100 parts by weight of the binding resin.

When using the titanyl phthalocyanine crystal alone as the electric charge generating material, the amount of the electric charge generating material is an amount of the titanyl phthalocyanine crystal. When using the titanyl phthalocyanine crystal in combination with the other electric charge generating material, the amount of the electric charge generating material is a total amount of them.

When using the titanyl phthalocyanine crystal in combination with the other electric charge generating material, the other electric charge generating material is preferably used in a small amount as far as the effect of the titanyl phthalocyanine crystal is not prevented. Specifically, the other electric charge generating material is preferably incorporated in the amount of 100 parts by weight or less based on 100 parts by weight of the titanyl phthalocyanine crystal.

When using only any one of the electron transferring material and hole transferring material as the electric charge transferring material, the amount of the electric charge transferring material is an amount of any one transferring material.

When using the electron transferring material in combination with the hole transferring material as the electric charge transferring material, the amount of the electric charge transferring material is a total amount of them.

When using the electron transferring material in combination with the hole transferring material, the electron transferring material is preferably incorporated in the amount within a range from 10 to 100 parts by weight based on 100 parts by weight of the hole transferring material.

A thickness of the single-layer type photosensitive layer is preferably within a range from about 5 to 100 μm, and particularly from about 10 to 50 μm.

A barrier layer may be formed between the conductive substrate and photosensitive layer in the photosensitive layer having a single-layer type photosensitive layer, whereas, the barrier layer may be formed between the conductive substrate and electric charge generating layer, or between the conductive substrate and electric charge transferring layer, or between the electric charge generating layer and electric charge transferring layer in the photosensitive layer having a multi-layer type photosensitive layer, as far as characteristics of the photosensitive material are prevented. A protective layer may be formed on the surface of the photosensitive material having the single-layer or multi-layer type photosensitive layer.

As the substrate on which the respective layers are formed, for example, various materials having the conductivity can be used. The substrate includes, for example, conductive substrates made of metals such as iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel and brass; substrates made of plastic materials prepared by depositing or laminating the above metals; and substrates made of glasses coated with aluminum iodide, tin oxide and indium oxide.

The substrate itself may have the conductivity, or the surface of the substrate may have the conductivity. The substrate may be preferably those having a sufficient mechanical strength on use.

The substrate may be in the form of a sheet or drum according to the structure of the image forming apparatus to be used.

When the respective layers constituting the photosensitive layer is formed by the coating method, a dispersion is prepared by dispersing and mixing the above electric charge generating material, electric charge transferring material and binding resin, together with the organic solvent such as tetrahydrofuran, using a known method such as roll mill, ball mill, attritor, paint shaker, and ultrasonic dispersing apparatus, and then the resulting dispersion is coated by using a known means and dried.

The organic solvent for preparing the coating solution for layer containing the titanyl phthalocyanine crystal, such as the single-layer type photosensitive layer and electric charge generating layer among the multi-layer type photosensitive layer include, for example, tetrahydrofuran, toluene, dichloromethane, 1,4-dioxane and a mixture thereof.

The organic solvent for preparing the coating solution for other layers includes, for example, alcohols such as methanol, ethanol, isopropanol and butanol; aliphatic hydrocarbons such as n-hexane, octane and cyclohexane; aromatic hydrocarbons such as benzene and xylene; halogenated hydrocarbons such as dichloroethane, carbon tetrachloride and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone and cylohexanone; esters such as ethyl acetate and methyl acetate; and dimethylformaldehyde, dimethylformamide, and dimethyl sulfoxide. These solvents can be used alone, or two or more kinds of them can be used in combination.

To improve the dispersion properties of the electric charge generating material and electric charge transferring material, and the smoothness of the surface of the photosensitive layer, for example, surfactants and leveling agents may be added.

EXAMPLES

The following Preparation Examples, Examples and Comparative Examples further illustrate the present invention in detail.

Titanyl Phthalocyanine Crystal Preparation Example 1

(Synthesis of Titanyl Phthalocyanine Compound)

In a flask wherein the atmosphere was replaced by argon, 25 g of 1,3-diiminoisoindoline, 22 g of titanium tetrabutoxide and 300 g of diphenylmethane were mixed and heated to 150° C.

While vapor generated in the flask was distilled out of the reaction system, the temperature in the system was raised to 215° C. Then, the mixture was reacted by stirring for additional four hours, with the temperature kept at 215° C .

After the completion of the reaction, the temperature in the system was cooled to 150° C. and the reaction mixture was filtered through a glass filter. The resulting solid was washed in turn with N,N-dimethylformamide and methanol, and then vacuum-dried to obtain 24 g of a violet solid.

(Pigmentation Pretreatment)

10 g of the violet solid obtained above was added in 100 ml of N,N-dimethylformamide, followed by a stirring treatment with heating to 130° C. for two hours.

After two hours have passed, heating was terminated and the reaction solution was cooled to room temperature (23±1° C. ) and stirring was also terminated. The solution was subjected to a stabilization treatment by allowing to stand in this state for 12 hours.

The stabilized solution was filtered through a glass filter, and then the resulting solid was washed with methanol and vacuum-dried to obtain 9.85 g of a crude crystal of a titanyl phthalocyanine.

(Pigmentation Treatment)

5 g of the crude crystal of the titanyl phthalocyanine obtained above was dissolved in 100 ml of a mixed solution of dichloromethane and trifluoroacetic acid (volume ratio: 4:1).

After the resulting solution was added dropwise in a mixed poor solvent of methanol and water (volume ratio: 1:1), the solution was stirred at room temperature for 15 minutes, and then allowed to stand at room temperature (23±1° C.) for 30 minutes, thereby to recrystallize the solution.

The solution was filtered through a glass filter. After washed with water until the wash becomes neutral without drying, the resulting solid was dispersed in 200 ml of chlorobenzene, with water contained therein, and then stirred for one hour.

The resulting solution was filtered through a glass filter and the resulting solid was vacuum-dried at 50° C. for five hours to obtain 4.2g of a non-substituted titanyl phthalocyanine crystal (blue powder) represented by the formula (11-1):

Preparation Example 2

(Acid-paste Method)

5 g of a crude crystal of the titanyl phthalocyanine compound synthesized in the same manner as in Preparation Example 1 and then subjected to the above pigmentation pretreatment, was dissolved in 1000 ml of a concentrated sulfuric acid.

After the resulting solution was added dropwise in water under ice-cooling, the solution was stirred for 15 minutes, and allowed to stand at room temperature (23±1° C.) for 30 minutes, thereby to recrystallize the solution.

(Milling Treatment)

The solution was filtered through a glass filter. After washed with water until the wash becomes neutral without drying, the resulting solid was dispersed in 200 ml of chlorobenzene, with water contained therein, and then stirred for one hour.

The resulting solution was filtered through a glass filter and the resulting solid was vacuum-dried at 50° C. for five hours to obtain 4.0 g of a non-substituted titanyl phthalocyanine crystal (blue powder) represented by the above formula (11-1).

Preparation Example 3

In the same manner as in Preparation Example 1, except that the pigmentation pretreatment was omitted, 4.2 g of a titanyl phthalocyanine crystal was obtained.

Preparation Example 4

In the same manner as in Preparation Example 1, except that the stirring treatment among the pigmentation pretreatment was conducted at room temperature (23±1° C.), 4.3 g of a titanyl phthalocyanine crystal was obtained.

Preparation Example 5

In the same manner as in Preparation Example 1, except that the stabilization treatment among the pigmentation pretreatment was omitted, 4.3 g of a titanyl phthalocyanine crystal was obtained.

Preparation Example 6

A titanyl phthalocyanine crystal was obtained according to Applied Preparation Example 1 described in Japanese Examined Patent Publication No. 2097121.

Namely, 2 g of non-crystalline titanyl phthalocyanine which was synthesized in the same manner as in Preparation Example 1 before pigmentation pretreatment was put in glass beaker, and then diethyleneglycoldimethylether was added therein until the total amount reached 200 ml.

Then, the resulting solution was stirred at room temperature (23±1° C.) for 24 hours, thereby to obtain a titanyl phthalocyanine crystal. Measurement of CuK α characteristic X-ray diffraction spectrum

A sample holder of a X-ray diffraction apparatus [RINT1100, manufactured by Rigaku Corporation] was filled with 0.5 g of each of titanyl phthalocyanine crystals immediately (within 60 minutes) after preparation obtained in the respective Preparation Examples and initial measurement was conducted.

0.5 g of each crystal was dispersed in 5 g of tetrahydrofuran and the solution was stored in a closed system under room temperature/normal humidity conditions of a temperature of 23±1° C. and a relative humidity of 50to 60% for 24 hours. Then, tetrahydrofuran was removed and additional measurement was conducted.

The conditions of the initial measurement and additional measurement are as follows.

X-ray tube: Cu

Tube voltage: 40 kV

Tube current: 30 mA

Start angle: 3.0°

Stop angle: 40.0°

Scanning rate: 10°/min.

Differential scanning calorimetry

Using a differential scanning calorimeter [Model TAS-200, DSC8230D, manufactured by Rigaku Corporation], the differential scanning calorimetry of the titanyl phthalocyanine crystals obtained in the respective Preparation Examples was conducted. The measurement conditions are as follows.

Sample pan: Al

Heating rate: 20° C./min.

The measurement results are shown in FIG. 1 to FIG. 18. The respective Preparation Examples correspond to the respective figures as shown in Table 1.

TABLE 1 CuKα characteristic Differential X-ray diffraction scanning Initial additional calorimetry measurement measurement Preparation FIG. 1 FIG. 2 FIG. 3 Example 1 Preparation FIG. 4 FIG. 5 FIG. 6 Example 2 Preparation FIG. 7 FIG. 8 FIG. 9 Example 3 Preparation FIG. 10 FIG. 11 FIG. 12 Example 4 Preparation FIG. 13 FIG. 14 FIG. 15 Example 5 Preparation FIG. 16 FIG. 17 FIG. 18 Example 6

It has been confirmed that the titanyl phthalocyanine crystal within 60 minutes after preparation, which is obtained in Preparation Example 1 has a strong peak at a Bragg angle 2θ±0.2°=9.5°, 24.1° and 27.2°, and has no peak at 26.2° as shown in FIG. 2; therefore, it has a Y type crystal form.

It has been confirmed that, even if the titanyl phthalocyanine crystal of Preparation Example 1 is dipped in tetrahydrofuran for 24 hours, no peaks appears at a Bragg angle 2θ±0.20°=26.2° and, therefore, the crystal retains a Y type crystal form and is not transferred to the other crystal forms such as β type.

It has been confirmed that the titanyl phthalocyanine crystal of Preparation Example 1 does not show a peak of a change in temperature within a range from 50 to 400° C. except for a peak at about 90° associated with evaporation of adsorbed water as shown in FIG. 1 and, therefore, the crystal hardly cause crystal transfer and is stable.

It has been confirmed that the titanyl phthalocyanine crystal within 60 minutes after preparation, which is obtained in Preparation Example 2 has a strong peak at a Bragg angle 2θ±0.2°=9.5°, 24.1° and 27.2°, and has no peak at 26.2° as shown in FIG. 5, and therefore, it also has a Y type crystal form.

It has been confirmed that, even if the titanyl phthalocyanine crystal of Preparation Example 2 is dipped in tetrahydrofuran for 24 hours, no peaks appears at a Bragg angle 2θ±0.2°=26.2° as shown in FIG. 6, and therefore, the crystal retains a Y type crystal form and is not transferred to the other crystal forms such as β type.

It has been confirmed that the titanyl phthalocyanine crystal of Preparation Example 2 does not show a peak of a change in temperature within a range from 50 to 400° C. except for a peak at about 90° associated with evaporation of adsorbed water as shown in FIG. 4, and therefore, the crystal hardly cause crystal transfer and is stable.

On the other hand, it has been confirmed that peak at a Bragg angle 2θ±0.2°=27.2° becomes small but a strong peak appeared at 26.2° by dipping any of the titanyl phthalocyanine crystals obtained in Preparation Examples 3 to 6 in tetrahydrofuran for 24 hours and, therefore, the crystals can not retain a Y type crystal form and are transferred to the β type.

It has been confirmed that any of the titanyl phthalocyanine crystals of Preparation Examples 3 to 6 show a peak at a temperature within a range from about 247to 260° C., in addition to a peak at about90° associated with evaporation of adsorbed water, in differential scanning calorimetry and, therefore, the crystal transfer occurs.

Single-layer Type Electrophotosensitive Material Examples 1 to 36

The titanyl phthalocyanine crystal obtained in Preparation Example 1 was used as the electric charge generating material.

5 Parts by weight of the titanyl phthalocyanine crystal, 70 parts by weight of a compound represented by any one of the formulas (HT-1) to (HT-17) as the hole transferring material, 30 parts by weight of a compound represented by any one of the formulas (ET-1) to (ET-6) as the electron transferring material, 100 parts by weight of polycarbonate as the binding resin and 800 parts by weight of tetrahydrofuran were mixed and dispersed using an ultrasonic dispersing apparatus to prepare a coating solution for single-layer type photosensitive layer.

Then, an aluminum substrate having a thickness of 1 mm as the conductive substrate was coated with the coating solution immediately after preparation within about 60 minutes using a wire bar, followed by hot-air drying at 110° C. for 30 minutes to produce an electrophotosensitive material having a single-layer type photosensitive layer of 25 μm in a film thickness.

After the above coating solution was stored in a closed system under the conditions of a temperature of 23±1° C. and a relative humidity of 50 to 60% for 24 hours and redispersed using an ultrasonic dispersing apparatus, an aluminum substrate was coated with the coating solution, followed by hot-air drying at 110° C. for 30 minutes to produce an electrophotosensitive material having a single-layer type photosensitive layer of 25 μm in a film thickness.

Examples 37 to 48

In the same manner as in Examples 1 to 12, except that the titanyl phthalocyanine crystal obtained in Preparation Example 2 was used as the electric charge generating material, a coating solution for single-layer type photosensitive layer was prepared.

Then, an aluminum substrate having a thickness of 1 mm as the conductive substrate was coated with the coating solution immediately after preparation within about 60 minutes using a wire bar, followed by hot-air drying at 110° C. for 30 minutes to produce an electrophotosensitive material having a single-layer type photosensitive layer of 25 μm in a film thickness.

After the above coating solution was stored in a closed system under the conditions of a temperature of 23±1° C. and a relative humidity of 50 to 60% for 24 hours and redispersed using an ultrasonic dispersing apparatus, an aluminum substrate was coated with the coating solution, followed by hot-air drying at 110° C. for 30 minutes to produce an electrophotosensitive material having a single-layer type photosensitive layer of 25 μm in a film thickness.

Comparative Examples 1 to 36

In the same manner as in Examples 1 to 36, except that the titanyl phthalocyanine crystal obtained in Preparation Example 3 was used as the electric charge generating material, a coating solution for single-layer type photosensitive layer was prepared.

Then, an aluminum substrate having a thickness of 1 mm as the conductive substrate was coated with the coating solution immediately after preparation within about 60 minutes using a wire bar, followed by hot-air drying at 110° C. for 30 minutes to produce an electrophotosensitive material having a single-layer type photosensitive layer of 25 μm in a film thickness.

After the above coating solution was stored in a closed system under the conditions of a temperature of 23±1° C. and a relative humidity of 50 to 60% for 24 hours and redispersed using an ultrasonic dispersing apparatus, an aluminum substrate was coated with the coating solution, followed by hot-air drying at 110° C. for 30 minutes to produce an electrophotosensitive material having a single-layer type photosensitive layer of 25 μm in a film thickness.

Comparative Examples 37 to 48

In the same manner as in Examples 1 to 12, except that the titanyl phthalocyanine crystal obtained in Preparation Example 6 was used as the electric charge generating material, a coating solution for single-layer type photosensitive layer was prepared.

Then, an aluminum substrate having a thickness of 1 mm as the conductive substrate was coated with the coating solution immediately after preparation within about 60 minutes using a wire bar, followed by hot-air drying at 110° C. for 30 minutes to produce an electrophotosensitive material having a single-layer type photosensitive layer of 25 μm in a film thickness.

After the above coating solution was stored in a closed system under the conditions of a temperature of 23±10° C. and a relative humidity of 50 to 60% for 24 hours and redispersed using an ultrasonic dispersing apparatus, an aluminum substrate was coated with the coating solution, followed by hot-air drying at 110° C. for 30 minutes to produce an electrophotosensitive material having a single-layer type photosensitive layer of 25 μm in a film thickness.

Sensitivity Characteristic Test (1)

Using a drum sensitivity tester, the photosensitive materials produced in the respective Examples and Comparative Examples were charged to a surface potential of +700 V by corona discharging.

The surface of each photosensitive material was irradiated with monochromic light having a wavelength of 780 nm (half-width: 20 nm, light intensity: 8 μW/cm²) through a band-pass filter for 1.5 seconds, and then a surface potential at the time at which 0.5 seconds have passed since the beginning of exposure was measured as a potential after exposure.

The sensitivity characteristics of the respective photosensitive materials were evaluated by a potential after exposure Vr₁ (V) of the electrophotosensitive material whose photosensitive layer was formed by using the coating solution immediately after preparation, and a potential after exposure Vr₂ (V) of the electrophotosensitive material whose photosensitive layer was formed by using the coating solution after storing for 24 hours.

The results are shown in Table 2 to Table 9.

TABLE 2 CGM HTM ETM Vr₁(V) Vr₂(V) Example 1 Preparation HT-1 ET-1 130 132 Example 1 Example 2 Preparation HT-6 ET-1 178 176 Example 1 Example 3 Preparation HT-7 ET-1 128 128 Example 1 Example 4 Preparation HT-9 ET-1 110 112 Example 1 Example 5 Preparation HT-12 ET-1 165 166 Example 1 Example 6 Preparation HT-13 ET-1 157 158 Example 1 Example 7 Preparation HT-14 ET-1 160 161 Example 1 Example 8 Preparation HT-2 ET-2 140 143 Example 1 Example 9 Preparation HT-5 ET-2 180 179 Example 1 Example 10 Preparation HT-10 ET-2 123 126 Example 1 Example 11 Preparation HT-15 ET-2 149 151 Example 1 Example 12 Preparation HT-16 ET-2 150 149 Example 1

TABLE 3 CGM HTM ETM Vr₁(V) Vr₂(V) Example 13 Preparation HT-3 ET-3 120 123 Example 1 Example 14 Preparation HT-7 ET-3 118 119 Example 1 Example 15 Preparation HT-9 ET-3  98 101 Example 1 Example 16 Preparation HT-11 ET-3 106 104 Example 1 Example 17 Preparation HT-15 ET-3 136 138 Example 1 Example 18 Preparation HT-17 ET-3 130 132 Example 1 Example 19 Preparation HT-3 ET-4 126 125 Example 1 Example 20 Preparation HT-4 ET-4 145 148 Example 1 Example 21 Preparation HT-8 ET-4 123 126 Example 1 Example 22 Preparation HT-11 ET-4 119 120 Example 1 Example 23 Preparation HT-13 ET-4 141 140 Example 1 Example 24 Preparation HT-16 ET-4 130 129 Example 1

TABLE 4 CGM HTM ETM Vr₁(V) Vr₂(V) Example 25 Preparation HT-1 ET-5 151 153 Example 1 Example 26 Preparation HT-4 ET-5 170 170 Example 1 Example 27 Preparation HT-6 ET-5 168 171 Example 1 Example 28 Preparation HT-11 ET-5 137 136 Example 1 Example 29 Preparation HT-14 ET-5 180 178 Example 1 Example 30 Preparation HT-17 ET-5 147 148 Example 1 Example 31 Preparation HT-2 ET-6 138 140 Example 1 Example 32 Preparation HT-3 ET-6 134 138 Example 1 Example 33 Preparation HT-7 ET-6 140 142 Example 1 Example 34 Preparation HT-10 ET-6 118 118 Example 1 Example 35 Preparation HT-15 ET-6 152 155 Example 1 Example 36 Preparation HT-17 ET-6 130 130 Example 1

TABLE 5 CGM HTM ETM Vr₁(V) Vr₂(V) Example 37 Preparation HT-1 ET-1 128 130 Example 2 Example 38 Preparation HT-6 ET-1 178 177 Example 2 Example 39 Preparation HT-7 ET-1 128 126 Example 2 Example 40 Preparation HT-9 ET-1 111 112 Example 2 Example 41 Preparation HT-12 ET-1 167 165 Example 2 Example 42 Preparation HT-13 ET-1 157 155 Example 2 Example 43 Preparation HT-14 ET-1 161 160 Example 2 Example 44 Preparation HT-2 ET-2 140 141 Example 2 Example 45 Preparation HT-5 ET-2 178 177 Example 2 Example 46 Preparation HT-10 ET-2 125 123 Example 2 Example 47 Preparation HT-15 ET-2 150 150 Example 2 Example 48 Preparation HT-16 ET-2 148 147 Example 2

TABLE 6 CGM HTM ETM Vr1(V) Vr₂(V) Comparative Preparation HT-1 ET-1 129 535 Example 1 Example 3 Comparative Preparation HT-6 ET-1 183 588 Example 2 Example 3 Comparative Preparation HT-7 ET-1 131 601 Example 3 Example 3 Comparative Preparation HT-9 ET-1 108 545 Example 4 Example 3 Comparative Preparation HT-12 ET-1 163 576 Example 5 Example 3 Comparative Preparation HT-13 ET-1 160 542 Example 6 Example 3 Comparative Preparation HT-14 ET-1 162 602 Example 7 Example 3 Comparative Preparation HT-2 ET-2 136 585 Example 8 Example 3 Comparative Preparation HT-5 ET-2 178 590 Example 9 Example 3 Comparative Preparation HT-10 ET-2 126 543 Example 10 Example 3 Comparative Preparation HT-15 ET-2 152 550 Example 11 Example 3 Comparative Preparation HT-16 ET-2 154 533 Example 12 Example 3

TABLE 7 CGM HTM ETM Vr₁(V) Vr₂(V) Comparative Preparation HT-3 ET-3 124 536 Example 13 Example 3 Comparative Preparation HT-7 ET-3 120 588 Example 14 Example 3 Comparative Preparation HT-9 ET-3 103 598 Example 15 Example 3 Comparative Preparation HT-11 ET-3 103 552 Example 16 Example 3 Comparative Preparation HT-15 ET-3 140 577 Example 17 Example 3 Comparative Preparation HT-17 ET-3 126 554 Example 18 Example 3 Comparative Preparation HT-3 ET-4 125 610 Example 19 Example 3 Comparative Preparation HT-4 ET-4 145 585 Example 20 Example 3 Comparative Preparation HT-8 ET-4 120 588 Example 21 Example 3 Comparative Preparation HT-11 ET-4 120 548 Example 22 Example 3 Comparative Preparation HT-13 ET-4 138 544 Example 23 Example 3 Comparative Preparation HT-16 ET-4 132 540 Example 24 Example 3

TABLE 8 CGM HTM ETM Vr₁(V) Vr₂(V) Comparative Preparation HT-1 ET-5 150 541 Example 25 Example 3 Comparative Preparation HT-4 ET-5 168 592 Example 26 Example 3 Comparative Preparation HT-6 ET-5 170 600 Example 27 Example 3 Comparative Preparation HT-11 ET-5 134 548 Example 28 Example 3 Comparative Preparation HT-14 ET-5 183 577 Example 29 Example 3 Comparative Preparation HT-17 ET-5 149 545 Example 30 Example 3 Comparative Preparation HT-2 ET-6 136 610 Example 31 Example 3 Comparative Preparation HT-3 ET-6 137 592 Example 32 Example 3 Comparative Preparation HT-7 ET-6 138 598 Example 33 Example 3 Comparative Preparation HT-10 ET-6 120 551 Example 34 Example 3 Comparative Preparation HT-15 ET-6 149 552 Example 35 Example 3 Comparative Preparation HT-17 ET-6 133 542 Example 36 Example 3

TABLE 9 CGM HTM ETM Vr₁(V) Vr₂(V) Comparative Preparation HT-1 ET-1 130 483 Example 37 Example 6 Comparative Preparation HT-6 ET-1 181 525 Example 38 Example 6 Comparative Preparation HT-7 ET-1 128 550 Example 39 Example 6 Comparative Preparation HT-9 ET-1 111 503 Example 40 Example 6 Comparative Preparation HT-12 ET-1 164 518 Example 41 Example 6 Comparative Preparation HT-13 ET-1 160 499 Example 42 Example 6 Comparative Preparation HT-14 ET-1 161 542 Example 43 Example 6 Comparative Preparation HT-2 ET-2 138 541 Example 44 Example 6 Comparative Preparation HT-5 ET-2 180 544 Example 45 Example 6 Comparative Preparation HT-10 ET-2 125 493 Example 46 Example 6 Comparative Preparation HT-15 ET-2 149 505 Example 47 Example 6 Comparative Preparation HT-16 ET-2 151 490 Example 48 Example 6

As is apparent from the tables described above, regarding the electrophotosensitive materials of Comparative Examples 1 to 48 using the titanyl phthalocyanine crystal of Preparation Examples 3 and 6, the potential after exposure Vr₂ (V) of the photosensitive material wherein the single-layer type photosensitive layer was formed using the coating solution stored for 24 hours after preparation was drastically increased as compared with the potential after exposure Vr₁ (V) of the photosensitive material wherein the single-layer type photosensitive layer was formed using the coating solution immediately after preparation. This fact showed that the sensitivity characteristics of the photosensitive material were drastically lowered by the storage of the coating solution in the titanyl phthalocyanine crystal of Preparation Examples 3 and 6.

On the other hand, regarding the electrophotosensitive materials Examples 1 to 48 using the titanyl phthalocyanine crystal of Preparation Examples 1 and 2 of the present invention, the potential after exposure Vr₁ (V) and the potential after exposure Vr₂ (V) were scarcely changed. This fact showed that the photosensitive material having good sensitivity characteristics, that are always stable regardless of the lapsed time after preparing the coating solution, by using the titanyl phthalocyanine crystal of Preparation Examples 1 and 2.

Multi-layer Type Electrophotosensitive Material Examples 49 to 65

The titanyl phthalocyanine crystal obtained in Preparation Example 1 was used as the electric charge generating material.

2.5 Parts by weight of the titanyl phthalocyanine crystal, 1 part by weight of polyvinyl butyral as the binding resin and 15 parts by weight of tetrahydrofuran were mixed and dispersed using an ultrasonic dispersing apparatus to prepare a coating solution for electric charge generating layer among a multi-layer type photosensitive layer.

Then, an aluminum substrate having a thickness of 1 mm as the conductive substrate was coated with the coating solution immediately after preparation within about 60 minutes using a wire bar, followed by hot-air drying at 110° C. for 30 minutes to form an electric charge generating layer of 0.5 μm in a film thickness.

1 part by weight of a compound represented by any one of the formulas (HT-1) to (HT-17) as the hole transferring material, 1 part by weight of polycarbonate as the binding resin and 10 parts by weight of toluene were mixed and dispersed using an ultrasonic dispersing apparatus to prepare a coating solution for electric charge transferring layer. Then, this coating solution was coated on the electric charge generating layer using a wire bar, followed by hot-air drying at 110° C. for 30 minutes to form an electric charge transferring layer of 20 μm in a film thickness, thus producing an electrophotosensitive material having a multi-layer type photosensitive layer.

After the above coating solution was stored in a closed system under the conditions of a temperature of 23±1° C. and a relative humidity of 50 to 60% for 24 hours and redispersed using an ultrasonic dispersing apparatus, an aluminum substrate was coated with the coating solution, followed by hot-air drying at 110° C. for 30 minutes to form an electric charge generating layer of 0.5 μm in a film thickness.

Then, the same coating solution for electric charge transferring layer was coated on the electric charge generating layer using a wire bar, followed by hot-air drying at 110° C. for 30 minutes to form an electric charge transferring layer of 20 μm in a film thickness, thus producing an electrophotosensitive material having a multi-layer type photosensitive layer.

Comparative Examples 49 to 65

In the same manner as in Examples 49 to 65, except that the titanyl phthalocyanine crystal obtained in Preparation Example 3 was used as the electric charge generating material, a coating solution for electric charge generating layer among a multi-layer type photosensitive layer was prepared.

Then, an aluminum substrate having a thickness of 1 mm as the conductive substrate was coated with the coating solution for electric charge generating layer immediately after preparation within about 60 minutes using a wire bar, followed by hot-air drying at 110° C. for 30 minutes to form an electric charge generating layer of 0.5 μm in a film thickness. Then, the same coating solution for electric charge transferring layer was coated on the electric charge generating layer using a wire bar, followed by hot-air drying at 110° C. for 30 minutes to form an electric charge transferring layer of 20 μm in a film thickness, thus producing an electrophotosensitive material having a multi-layer type photosensitive layer.

After the above coating solution was stored in a closed system under the conditions of a temperature of 23±1° C. and a relative humidity of 50 to 60% for 24 hours and redispersed using an ultrasonic dispersing apparatus, an aluminum substrate was coated with the coating solution, followed by hot-air drying at 110° C. for 30 minutes to form an electric charge generating layer of 0.5 μm in a film thickness.

Then, the same coating solution for electric charge transferring layer was coated on the electric charge generating layer using a wire bar, followed by hot-air drying at 110° C. for 30 minutes to form an electric charge transferring layer of 20 μm in a film thickness, thus producing an electrophotosensitive material having a multi-layer type photosensitive layer.

Sensitivity Characteristic Test (2)

Using a drum sensitivity tester, the photosensitive materials produced in the respective Examples and Comparative Examples were charged to a surface potential of −700 V by corona discharging.

The surface of each photosensitive material was irradiated with monochromic light having a wavelength of 780 nm (half-width: 20 nm, light intensity: 8 μW/cm²) through a band-pass filter for 1.5 seconds, and then a surface potential at the time at which 0.5 seconds have passed since the beginning of exposure was measured as a potential after exposure.

The sensitivity characteristics of the respective photosensitive materials were evaluated by a potential after exposure Vr₁ (V) of the electrophotosensitive material whose electric charge generating layer was formed by using the coating solution immediately after preparation, and a potential after exposure Vr₂ (V) of the electrophotosensitive material whose electric charge generating layer was formed by using the coating solution after storing for 24 hours. The results are shown in Table 10 and Table 11.

TABLE 10 CGM HTM Vr₁(V) Vr₂(V) Example 49 Preparation HT-1 −132 −133 Example 1 Example 50 Preparation HT-2 −110 −111 Example 1 Example 51 Preparation HT-3 −265 −265 Example 1 Example 52 Preparation HT-4 −115 −117 Example 1 Example 53 Preparation HT-5 −178 −177 Example 1 Example 54 Preparation HT-6 −142 −144 Example 1 Example 55 Preparation HT-7 −110 −112 Example 1 Example 56 Preparation HT-8 −114 −111 Example 1 Example 57 Preparation HT-9  −92  −95 Example 1 Example 58 Preparation HT-10 −95 −99 Example 1 Example 59 Preparation HT-11 −112 −115 Example 1 Example 60 Preparation HT-12 −124 −125 Example 1 Example 61 Preparation HT-13 −152 −153 Example 1 Example 62 Preparation HT-14 −155 −157 Example 1 Example 63 Preparation HT-15 −144 −145 Example 1 Example 64 Preparation HT-16 −140 −140 Example 1 Example 65 Preparation HT-17 −133 −136 Example 1

TABLE 11 CGM HTM Vr₁(V) Vr₂(V) Comparative Preparation HT-1 −131 −570 Example 49 Example 3 Comparative Preparation HT-2 −112 −555 Example 50 Example 3 Comparative Preparation HT-3 −267 −601 Example 51 Example 3 Comparative Preparation HT-4 −120 −558 Example 52 Example 3 Comparative Preparation HT-5 −177 −586 Example 53 Example 3 Comparative Preparation HT-6 −144 −575 Example 54 Example 3 Comparative Preparation HT-7 −111 −557 Example 55 Example 3 Comparative Preparation HT-8 −117 −601 Example 56 Example 3 Comparative Preparation HT-9  −95 −544 Example 57 Example 3 Comparative Preparation HT-10 −100 −589 Example 58 Example 3 Comparative Preparation HT-11 −114 −548 Example 59 Example 3 Comparative Preparation HT-12 −122 −552 Example 60 Example 3 Comparative Preparation HT-13 −155 −583 Example 61 Example 3 Comparative Preparation HT-14 −155 −587 Example 62 Example 3 Comparative Preparation HT-15 −145 −582 Example 63 Example 3 Comparative Preparation HT-16 −141 −579 Example 64 Example 3 Comparative Preparation HT-17 −133 −570 Example 65 Example 3

As is apparent from the tables described above, regarding the electrophotosensitive materials of Comparative Examples 49 to 65 using the titanyl phthalocyanine crystal of Preparation Example 3, the potential after exposure Vr₂ (V) of the photosensitive material wherein the electric charge generating layer was formed using the coating solution stored for 24 hours after preparation was drastically increased as compared with the potential after exposure Vr₁ (V) of the photosensitive material wherein the electric charge generating layer was formed using the coating solution immediately after preparation. This fact showed that the sensitivity characteristics of the photosensitive material were drastically lowered by the storage of the coating solution in the titanyl phthalocyanine crystal of Preparation Example 3.

On the other hand, regarding the electrophotosensitive materials Examples 49 to 65 using the titanyl phthalocyanine crystal of Preparation Example 1 of the present invention, the potential after exposure Vr₁ (V) and the potential after exposure Vr₂ (V) were scarcely changed. This fact showed that the photosensitive material having good sensitivity characteristics, that are always stable regardless of the lapsed time after preparing the coating solution, by using the titanyl phthalocyanine crystal of

Preparation Example 1. Stability Test After Isolation

Each of the photosensitive layers were peeled off from the single-layer type electrophotosensitive materials produced in Example 1 and Comparative Example 1 and then dissolved in tetrahydrofuran under the conditions of a temperature of 23±1° C. and a relative humidity of 50 to 60%.

After a titanyl phthalocyanine crystal was isolated by filtering the resulting solution, the CuK α characteristic X-ray diffraction of the titanyl phthalocyanine crystal immediately after isolation and that of the titanyl phthalocyanine crystal recovered after isolating from the photosensitive layer and dispersing and dipping in tetrahydrofuran for 24 hours under the conditions of a temperature of 23±1° C. and a relative humidity of 50 to 60% in a closed system were measured respectively in the same manner as described above.

The measurement results are shown in FIG. 19 to FIG. 22. The respective samples correspond to the respective figures as shown below.

TABLE 12 CuKα characteristic Titanyl X-ray diffraction phthalocyanine immediately after Crystal after isolation recovery Example 1 Preparation FIG. 19 FIG. 20 Example 1 Comp. Preparation FIG. 21 FIG. 22 Example 1 Example 3

As is apparent from the results of FIG. 19 and FIG. 20, the titanyl phthalocyanine crystal isolated from the single-layer type electrophotosensitive layer of Example 1 has a strong peak at a Bragg angle 2θ±0.2°=27.2°, but has no peak at 26.2° in any case of immediately after isolation and dipping after 24 hours. As a result, it was confirmed that the titanyl phthalocyanine crystal of Preparation Example 1 used in the photosensitive material of Example 1 can retain the crystal form stably even after the production of the photosensitive material.

As is apparent from the results of FIG. 21 and FIG. 22, the titanyl phthalocyanine crystal isolated from the single-layer type electrophotosensitive material of Comparative Example 1 has a strong peak at a Bragg angle 2θ±0.2°=27.2°, but has no peak at 26.2° only in case of immediately after isolation. However, the intensity of the peak at a Bragg angle 2θ±0.2°=26.2° increased to 410% of that of the peak at 27.2° after dipping for 24 hours. As a result, it was confirmed that the titanyl phthalocyanine crystal of Preparation Example 3 used for the photosensitive material of Comparative Example 1 can not be retained stably in tetrahydrofuran after the production of the photosensitive material.

The disclosure of japanese patent application Serial No. 11-292690, filed on Oct. 14, 1999, is incorporated herein by reference. 

What is claimed is:
 1. A titanyl phthalocyanine crystal formed by crystallizing a titanyl phthalocyanine compound, characterized in that the titanyl phthalocyanine crystal does not have a peak of a change in temperature within a range from 50 to 400° C. except for a peak associated with evaporation of adsorbed water in differential scanning calorimetry.
 2. The titanyl phthalocyanine crystal according to claim 1, which is formed from a titanyl phthalocyanine compound represented by the formula (1):

wherein X¹, X², X³ and X⁴ are the same or different and each represents a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group, and a, b, c and d are the same or different and each represents an integer of 0 to 4, and which has at least a maximum peak at a Bragg angle 2θ±0.2°=27.2° and has no peak at 26.2° in a CuK α characteristic X-ray diffraction spectrum.
 3. The titanyl phthalocyanine crystal according to claim 2, which is formed from a titanyl phthalocyanine compound represented by the formula (11):

wherein X represents a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group, and e represents an integer of 0 to
 4. 4. The titanyl phthalocyanine crystal according to claim 3, which is formed from a titanyl phthalocyanine compound represented by the formula (11-1).


5. The titanyl phthalocyanine crystal according to claim 2, wherein a crystal recovered after dipping in an organic solvent for 24 hours has at least a maximum peak at a Bragg angle 2θ±0.2°=27.2° and has no peak at 26.2° in a CuK α characteristic X-ray diffraction spectrum.
 6. The titanyl phthalocyanine crystal according to claim 5, wherein the organic solvent is at least one selected from the group consisting of tetrahydrofuran, dichloromethane, toluene and 1,4-dioxane.
 7. The titanyl phthalocyanine crystal according to claim 1, which is produced by the following steps: a pigmentation pretreatment step of adding a titanyl phthalocyanine in an aqueous organic solvent, stirring under heating for a fixed time, and allowing the resulting solution to stand for a fixed time under the conditions at a temperature lower than that of the above stirring process, thereby to stabilize the solution; and a pigmentation step of removing the aqueous organic solvent from the solution to obtain a crude crystal of the titanyl phthalocyanine, dissolving the crude crystal of the titanyl phthalocyanine in a solvent, adding dropwise the solution in a poor solvent to recrystallize the titanyl phthalocyanine compound, and then subjecting the recrystallized compound to milling treatment in a non-aqueous solvent, with water contained therein.
 8. The titanyl phthalocyanine crystal according to claim 1, which is produced by the following steps: a pigmentation pretreatment step of adding a titanyl phthalocyanine in an aqueous organic solvent, stirring under heating for a fixed time, and allowing the resulting solution to stand for a fixed time under the conditions at a temperature lower than that of the above stirring process, thereby to stabilize the solution; a step of removing the aqueous organic solvent from the solution to obtain a crude crystal of the titanyl phthalocyanine, and treating the crude crystal of the titanyl phthalocyanine according to acid-paste method; and a step of subjecting a low-crystalline titanyl phthalocyanine compound obtained by the above step to milling treatment, with water contained therein.
 9. A titanyl phthalocyanine crystal formed by crystallizing a titanyl phthalocyanine compound, characterized in that a crystal recovered after dipping in an organic solvent for 24 hours has at least a maximum peak at a Bragg angle 2θ±0.2°=27.2° and has no peak at 26.2° in a CuK α characteristic X-ray diffraction spectrum.
 10. The titanyl phthalocyanine crystal according to claim 9, wherein the organic solvent is at least one selected from the group consisting of tetrahydrofuran, dichloromethane, toluene and 1,4-dioxane.
 11. A method of producing the titanyl phthalocyanine crystal of claim 1, which comprises the following steps: a pigmentation pretreatment step of adding a titanyl phthalocyanine in an aqueous organic solvent, stirring under heating for a fixed time, and allowing the resulting solution to stand for a fixed time under the conditions at a temperature lower than that of the above stirring process, thereby to stabilize the solution; and a pigmentation step of removing the aqueous organic solvent from the solution to obtain a crude crystal of the titanyl phthalocyanine, dissolving the crude crystal of the titanyl phthalocyanine in a solvent, adding dropwise the solution in a poor solvent to recrystallize the titanyl phthalocyanine compound, and then subjecting the recrystallized compound to milling treatment in a non-aqueous solvent, with water contained therein.
 12. A method of producing the titanyl phthalocyanine crystal of claim 1, which comprises the following steps: a pigmentation pretreatment step of adding a titanyl phthalocyanine in an aqueous organic solvent, stirring under heating for a fixed time, and allowing the resulting solution to stand for a fixed time under the conditions at a temperature lower than that of the above stirring process, thereby to stabilize the solution; a step of removing the aqueous organic solvent from the solution to obtain a crude crystal of the titanyl phthalocyanine, and treating the crude crystal of the titanyl phthalocyanine according to acid-paste method; and a step of subjecting a low-crystalline titanyl phthalocyanine compound obtained by the above step to milling treatment, with water contained therein.
 13. A method of producing the titanyl phthalocyanine crystal of claim 9, which comprises the following steps: a pigmentation pretreatment step of adding a titanyl phthalocyanine in an aqueous organic solvent, stirring under heating for a fixed time, and allowing the resulting solution to stand for a fixed time under the conditions at a temperature lower than that of the above stirring process, thereby to stabilize the solution; and a pigmentation step of removing the aqueous organic solvent from the solution to obtain a crude crystal of the titanyl phthalocyanine, dissolving the crude crystal of the titanyl phthalocyanine in a solvent, adding dropwise the solution in a poor solvent to recrystallize the titanyl phthalocyanine compound, and then subjecting the recrystallized compound to milling treatment in a non-aqueous solvent, with water contained therein.
 14. A method of producing the titanyl phthalocyanine crystal of claim 9, which comprises the following steps: a pigmentation pretreatment step of adding a titanyl phthalocyanine in an aqueous organic solvent, stirring under heating for a fixed time, and allowing the resulting solution to stand for a fixed time under the conditions at a temperature lower than that of the above stirring process, thereby to stabilize the solution; a step of removing the aqueous organic solvent from the solution to obtain a crude crystal of the titanyl phthalocyanine, and treating the crude crystal of the titanyl phthalocyanine according to acid-paste method; and a step of subjecting a low-crystalline titanyl phthalocyanine compound obtained by the above step to milling treatment, with water contained therein. 